bootloader and memory usage

Greetings,
  When a program is too big to fit on a microcontoller internal memroy,
external memory has to be used.  Thats when a bootloader is needed.
  Does a bootloader go hand in hand with an RTOS or is it sometimes
used to without one? Also, what kind of memory is typically used in
this setting, and how is it updated?

Thank you for your input.
-- a

amerdsp wrote:
> Greetings,
>   When a program is too big to fit on a microcontoller internal memroy,
> external memory has to be used.  Thats when a bootloader is needed.
>   Does a bootloader go hand in hand with an RTOS or is it sometimes
> used to without one? Also, what kind of memory is typically used in
> this setting, and how is it updated?
> 
> Thank you for your input.
> -- a
> 
This brings up more questions.

A bootloader may or may not use a RTOS.
An RTOS may or may not be able to use a bootloader.

A microcontroller with internal memory must be able to write its own 
FLASH ROM.

So, which microcontroller do you have in mind ??

Please give more information, an we can give a better answer.

amerdsp wrote:

> Greetings,
>   When a program is too big to fit on a microcontoller internal memroy,
> external memory has to be used.  Thats when a bootloader is needed.

Bootloader is a piece of code which typically does the following:

1. Reprogramming the system flash memory with the external data.
2. Doing all necessary initializations and launching the application code.

>   Does a bootloader go hand in hand with an RTOS or is it sometimes
> used to without one?

No connection. The bootloader may be used with or without RTOS. RTOS may 
or may not use the bootloader.

> Also, what kind of memory is typically used in
> this setting, and how is it updated?

Flash.


Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

http://www.abvolt.com

amerdsp <amerdsp@hotmail.com> wrote:

>   When a program is too big to fit on a microcontoller internal memroy,
> external memory has to be used.  

Not necessarily.  A micro with more internal memory may work just as
well, if it's available.

> Thats when a bootloader is needed.

No.  You only need a bootloader if the external memory isn't directly
readable as code by the CPU, or if you want to be able to have
multiple codes among which the bootloader has to select, for purposes
like in-application program updates.

>   Does a bootloader go hand in hand with an RTOS or is it sometimes
> used to without one? 

Again, apples and oranges.

> Also, what kind of memory is typically used in this setting, and how
> is it updated?

Depends on whether you actually needed a bootloader or not.  Parallel
flash or (more rarely) OTP for applications without a bootloader, any
kind of storage you can imagine for those with one.  The weirdest
boot-loading scenario I've seen involved a HP Unix workstation booted
off a tape drive.

-- 
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

> A microcontroller with internal memory must be able to write its own
> FLASH ROM.
>
> So, which microcontroller do you have in mind ??
>
> Please give more information, an we can give a better answer.

I do not have any microcontroller in mind.  What I was asking about is
that if the program does not fit in the internal memory, an external
memory can be used.  How is this external memory is usually updated?

Thanks

-- a

amerdsp wrote:
>>A microcontroller with internal memory must be able to write its own
>>FLASH ROM.
>>
>>So, which microcontroller do you have in mind ??
>>
>>Please give more information, an we can give a better answer.
> 
> 
> I do not have any microcontroller in mind.  What I was asking about is
> that if the program does not fit in the internal memory, an external
> memory can be used.  How is this external memory is usually updated?
> 
> Thanks
> 
> -- a
> 
Well, there is no answer to this question.

If this were a product with a real schedule, getting a part of the next 
higher size would be used. ( been there, done that)

If this is a hobby project, then does the microcontroller have an 
external memory interface.

Most of the current crop of microcontrollers do not have external memory 
interfaces.

Only internal memory. PIC, MSP, AVR, all these deviced do NOT have 
external memory interfaces.

So, with out knowledge of the microcontroller you want to use, this 
question can not be answered.


Now, if you are using an micro_processor, then there may be an answer.

So, check the data sheet of what ever chip you have in mind.
That will be the only way to tell if this can be done at all.

Good Luck.

amerdsp wrote:
> Greetings,
>   When a program is too big to fit on a microcontoller internal memroy,
> external memory has to be used. 
That statement Is not Always true (if Ever)
Single chip micros often have bootloaders to program the internal Flash.
The boot loader to prgram internal and external would need to be more 
sophisticated to program two kinds of memory.

  Thats when a bootloader is needed.
>   Does a bootloader go hand in hand with an RTOS or is it sometimes
> used to without one?
Bootloader go with many types of Flash micros.  The RTOS is usually not 
involved.  The RTOS jumps to the bootloader as it usually can not run 
during the programming.

  Also, what kind of memory is typically used in
> this setting, and how is it updated?

Usually Flash, but other types of in circuit programmable memory, as 
well as battery backed memory can be used.
> 
> Thank you for your input.
> -- a
>